查找相同数字并用新数字替换其他数字

Question

I have 2 arrays (both containing 2 strings each) one contains serial numbers from a USB. the other contains serial numbers from a text file. I was able to retrieve them both successfully. So here's my problem: I need to compare them to each other, find exactly one serial number that differs, and replace it. like this:

Contents (Dummy Serial numbers)
     ________
USB | A | B

TXT | B | C

As you can see, the USB and TXT array both contain one of the same serial number (B). That part is easy; I however need to write code to see that C != A and then I need A to replace C.

I tried this:

for (int x = 0; x < 2; x++)
{
     for (int y = 0; y < 2; y++)
     {
          //checks for same serial number
          if (m_AttachedUSB[x] == m_Existing_Serial_Numbers[y])
          {
              //found one
              IntOnlyOne++;
              //we want this one to stay beacause it has a serial number 
              //that matches one in the .txt file
              m_ChachedUSB = m_AttachedUSB[x];
          }
     }
}

This however only finds the serial numbers that are similar. How do I replace the ones that are different?

Answer 1

If I understood you right:

List<int> usb = new List<int> {1,2,4,7,8};
List<int> text = new List<int> {1,2,3,4,5};

usb.Intersect(text).Union(usb);

That will return a list containing {1,2,4,7,8}.

The intersect method gives you all items that are contained by both lists. In this case {1,2,4}. The union method will join all items from usb when they are not yet available. In this case {7,8}.

Answer 2

The following creates a set of all the serial numbers in the USB list, then loops through the TXT list, either removing a matching item from the USB set or noting the index of an "old" item in the TXT list.

It then replaces the "old" items with the remaining items in the USB set, which should be now just be the "new" items.

This assumes that both lists are the same length, and that the USB list contains no duplicates.

HashSet<string> usbSNs = new HashSet<string>(m_AttachedUSB); // { "A", "B" }
List<int> txtOldIndices = new List<int>();                   // { }

// Remove existing items from USB set, note indices of old items in TXT list.
for (int i = 0; i < m_CachedUSB.Length; i++)
{                                         // First iteration  Second iteration
    if (!usbSNs.Remove(m_CachedUSB[i]))   // Now { "A" }      Still { "A" }
        txtOldIndices.Add(i);             // Still {}         Now { 1 }
}
// At this point you may want to check usbSNs and txtOldIndices
// have the same number of elements.

// Overwrite old items in TXT list with remaining, new items in USB set.    
foreach(var newSN in usbSNs)
{
    m_CachedUSB[txtOldIndices[0]] = newSN;    // Now [ "B", "A" ]
    txtOldIndices.RemoveAt(0);                // Now { }
}

Essentially, this is a way of copying m_AttachedUSB over m_CachedUSB , while preserving the locations of items which are common to both, which is what I assumed you were going for.

Answer 3

With only 4 items in your lists you can keep it simple:

if(usbArray[0] == textArray[0])
  usbArray[1] = textArray[1];
else if(usbArray[0] == textArray[1])
  usbArray[1] = textArray[0];
else if(usbArray[1] == textArray[0])
  usbArray[0] = textArray[1];
else if(usbArray[1] == textArray[1])
  usbArray[0] = textArray[0];

Basically, change the two that are different.

And a second solution:

for(int i=0; i<=1; i++)
  for(int j=0; j<=1; j++)
     if(usbArray[i] == textArray[j])
       usbArray[(i+1)%2] = textArray[(j+1)%2];